A great effort has been made to develop technologies for cast molding of hydrogel contact lenses with high precision, fidelity and reproducibility and at low cost. One of such manufacturing technologies is the so-called Lightstream Technology™ (Alcon) involving reusable molds and curing a lens-forming composition under a spatial limitation of actinic radiation (U.S. Pat. Nos. 5,508,317, 5,583,163, 5,789,464, 5,849,810, and 8,163,206). The Lightstream Technology™ for making contact lenses have several advantages. For example, reusable quartz/glass molds or/and reusable plastic molds, not disposable plastic molds, can be used, because, following the production of a lens, these molds can be cleaned rapidly and effectively of the uncrosslinked monomer or prepolymer and other residues, using a suitable solvent and can be blown dried with air. Disposable plastic molds inherently have variations in the dimensions, because, during injection-molding of plastic molds, fluctuations in the dimensions of molds can occur as a result of fluctuations in the production process (temperatures, pressures, material properties), and also because the resultant molds may undergo non-uniformly shrinking after the injection molding. These dimensional changes in the mold may lead to fluctuations in the parameters of contact lenses to be produced (peak refractive index, diameter, base curve, central thickness etc.) and to a low fidelity in duplicating complex lens design. By using reusable molds which are produced in high precision, one can eliminate dimensional variations inherently presented in disposable molds and thereby variation in contact lenses produced therefrom. Lenses produced according to the Lightstream Technology™ can have high consistency and high fidelity to the original lens design.
However, modern high-volume mass production process for medical devices like contact lenses utilizes re-usable molds in each production cycles. A pre-requisite that molds could be re-usable is that they have equivalent and reproducible clean surface properties in each production cycles. Especially the cleaning of molds utilized for the production of silicon hydrogel contact lenses by the Lightstream technology is very challenging: the molds are made of glass and quartz, i.e. have a high surface energy and are therefore easily deposited by the silicon compounds with their low surface energy utilized for the lens production.
This silicon compounds could be cleaned-off easily in laboratory by organic solvents like 2-Propanol. But for high mass-production process like the Lightstream technology an organic solvent based cleaning process is difficult to realize. Safety, environmental and consumption aspects in combination with high process times needed for solvent removing and rinsing prevents such an application. Therefore would be a water based cleaning process the best for such a process.
Therefore, there is still a need for new reusable molds that can be easily cleaned with water based cleaning process.